Such a coupling is known from DE 10141315 C1. The previously known coupling possesses a coupling part into which an insertion section of a counterpart can be inserted. Also present is a C-˜shaped locking part which is mounted on the coupling part so that it can rotate around the longitudinal axis of the coupling. As the detent structure, the locking part possesses sections which are like segments of a circle and which in a detent position interact, through the fact that they engage in recesses configured on the coupling part and the insertion section, with a complementary structure configured on the insertion segment for locking the counterpart and the coupling part in a locking position. When the locking part is rotated around the longitudinal axis of the coupling, the sections which are like segments of a circle slide out of the recesses while bending the locking part upward, and release the insertion section in a release position. To facilitate the rotation, gripping grooves or nubs are present on the outside of the locking part.
When operating the previously known coupling, however, in a certain sense it turned out to be disadvantageous that the release position exhibited a certain instability, since under the effect of a relatively low force on the coupling part, the latter changes over directly from the release position into the locking position in an abrupt fashion. In addition, the transfer of the coupling part from the locking position into the release position by rotating it has not proven to be optimal because of the relatively large amount of space required for doing this. Finally, performing the rotating movement with a locking part having smooth walls, after the gripping grooves or nubs have worn off, for example, is sometimes not without problems.